Refrigeration system including evaporator defrosting means



i s. P. SOLING 430,960

REFRIGERATON SYSTEM INCLUDING EVAPOHATOR DEFROSTING MEANS Filed May 29. 1945 Fil l N ORMALLV CLD SED EVAPORATOR.

CONDEMSER,

i To suc'x'xom cowmac'nom F16 2 or COMPRESSOR;

nventor Samul Pl Song Gttornegs Patented Nov. 18, 1947 REFRIGERATION SYSTEM INCLUDING EVAPORATOR DEFROSTING NIEANS Samuel l. Soling, York, Pa., assignor to York Corporation, York, Pa., a corporation of Dela- Ware Application May 29, 1945, Serial No. 596,523

5 Claims. l

This invention relates to refrigeration and particularly to means operable periodically to defrost an evaporator which is normally operated at sub-freezing temperatures.

From the early days of mechanical refrigeration it has been common practice to defrost. evaporators by what is called the hot gas method, that is to say by causingthe compressor.

to deliver hot compressed gas to the evaporator. The successful use of this, as heretofore commonly carried out, depends on Ithe presence in the refrigerative circuit of more than one evaporator, or an evaporator capable of subdivision into units which are defrosted one at a time, so that the condenser may continue to function.

In defrosting systems having a-single evaporator, recourse has been had usually to some type of heater. These heaters have been of various types and variously located. They are expensive and consume valuable energy.

The present invention is applicable to systems having a single evaporator, resembles and has all the advantages of the conventional hot gas method, and avails of Waste heat accumulated externally of the circuit to furnish the heat units needed to thaw the frost.

Generally stated the invention contemplates a heat accumulator which is `external to the circuit, and which accumulates heat in substantial quantity but usually at moderate temperature. Such an accumulator may be charged with spent (hot) condenser cooling water, or may he a liquid bath heated by waste heat Ifrom the compressor cylinders or from the motor or :motors which drive the compressor or other apparatus. Since the accumulator is external to the circuit it does not impair or limit normal performance of the reirigerative circuit.

When defi-ostina is desired, two connections are temporarily established while the compressor` runs, the first being a hot gas connection from the compressor discharge to the vapor space in the evaporator, and the second being made up of a drain connection from the liquid space of the evaporator to a heat exchanger in the heat accumulator, and a suction connection thence to the intake of the compressor.

Thus hot vaporofus refrigerant from the com- 2 store sumcient heat for one defrosting cycle at the rather low temperatures at which waste heat is commonly available. The higher the temperature at which waste head is available, the smaller is the needed storage capacity. After all, every heat exchanger has some heat storage capacity, so both functions are always present. How they are proportioned is a matter of design, commonly controlled by the maximum temperature at which some part of the apparatus may b'e operated. For example, the pere Fig. 2 is a fragmentary view showing howl waste heat may be recovered from a motor-compressor unit instead of from spent condenser Fig. 3 is a fragmentary view showing another modification.

Refer first to Fig. l. The compressor is shown at 5 and is driven by an electric motor G through a. belt. The high pressure gas line 'I (discharge line) leads to a water-cooled condenser-receiver 8. This is of the shell-and-tub'e type in which the water `flows through the tubes and the refrigerant condenses outside the tubes. Thus the condensed refrigerant flows to the liquid line 9.

The water-supply connection is indicated at II, and the water-discharge connection at- I2. Connection I2 leads to the accumulator shell I3 and the condenser water nnally discharges from `the shell I3 through the connection I4. Contype having a thermal bulb I'I. Expansion valve I 6 supplies refrigerant to an evaporator I 8 diagrammed as a simple sinuous coil. In normal operation the thermal bulb I1, which is applied to the suction connection I3, caluses the valve I to supply refrigerant to the evaporator I3 at such a rate that fthe oil-flowing vapor is always slightly superheated. The evaporator suction line I9 is connected to the compressor suction line 2| through a normallyvopen valve 22. The valve 22 is operated by a solenoid 23. When the solenoid 23 is energized the valve 22 is closed.

The branch 24 of the line I9 leads to one end of the coil I5, whose other end is connected by the line 25 with the compressor suction line 2|. When the valve 22 is open, flow will occur through the valve 22 and substantially no ow through the coil I5 will occur because there is substantial resistance to the flow 'through the coil. This makes it unnecessary to use a three-way valve to insure alternate flow from I9 directly to 2|, or fromIS through I5 to 2|.` To all intents and purposes, the opening and closing of the valve 22 produces strictly selective flow.

A branch line 26 leads from the high-pressure gas line 1 through a normally closed valve 21 to the vapor space in the evaporator I8. The valve 7:1 is operated by a solenoid 28. The valve opens when the solenoid 28 is energized.

'I'he lines which supply current to the motor 6 and to the solenoids 23 and 28 are shown at 3| and 32. The motor is controlled by a switch 33. The solenoids are controlled by a switch 34 which is independently operable. When the switch 34 is open the valve 22 is open and the valve 21 is closed. When the switch 34 is closed the valve 22 closes and the valve 21 opens.

The switch 34 may be manually operated, or if periodic defrosting is desired it can be operated by a clock. There are various other known expedients in the art for initiating defrosting, and various of these may be used.

Assume that the plant has been in operation, that the evaporator I8 has become frosted, and that it is desired to defrost it. The switch 33 remains closed and the switch 34 is closed. 'I'he opening of the valve 21 causes the compressor to deliver hot gas to the vapor space in the evaporator I8. The refrigerant gives up its heat and condenses, and the heat thus released melts the frost off the evaporator. The liquid refrigerant drains from the evaporator, through the line I9, and since the valve 22 is closed, flows through the connection 24 to the heat-exchanger coil I5 and thence, in the vapor phase, through the lines 25 and 2| to the compressor. 'I'he warm condenser water in the shell I3 evaporates the liquid refrigerant entering coil I5. so that only vaporous refrigerant is drawn into the compressor.

When the defrosting operation is complete the switch 34 is again opened, restoring the system to its normal refrigerating cycle. If any liquid refrigerant should remain in the coil I5, it will be evaporated and withdrawn by the compressor. In anycase, the opening of the valve 22 virtually suspends flow through the coil I5, so that the coil I5 is external to the refrigerative circuit and exercises no disturbing effect thereon. This is an important aspect of the invention.

Fig. 2 is a fragmentary view showing a heat recovery means which may be substituted for the shell I3 and coil I5. In this view parts identical with parts in Fig. 1 are identified by the same reference numerals and the distinguishing letter a.

The device indicated at 3| is an enclosed motor-compressor unit, in which a certain amount 4 of mechanical energy degenerates into heat. In such a unit some of the heat is derived from the motor and some from the compressor. Surrounding unit 3| is a cooling jacket 32 connected in a thermosiphon circuit with shell 33 by the pipes 34, 35. Thus coil I5a, the direct analog of coil I5, is subject to heat available at rather low temperature in shell 33.

The motor-compressor unit replaces the motor 6 and compressor 5, but to avoid confusing Fig. 2, connections analogous to 1. 2| 26 of Fig. l are not illustrated.

Both Fig. l and Fig. 2 show liquid baths which accumulate heat but in some cases this extra heat storage capacity is unnecessary, either because heat is available in adequate quantity or because the motor-compressor itself offers adequate heat storage capacity. In such a case the jacket 32 can be connected to perform the function of coil I5a of Fig. 2 as suggested in Fig. 3.

In Fig. 3 parts identica1 with parts in Figs. l and 2 bear the same reference numerals with the letter b.' The motor-compressor is indicated at |3| andits jacket at |32.

'I'hree embodiments have been illustrated and others are possible. The invention contemplates that waste heat accumulated in adequate quantity at a safe temperature shall be used to supply the heat for defrosting and to protect the compressor against entry of refrigerant in the liquid phase while defrosting proceeds. This waste heat is accumulated outside the refrigerating circuit, which is a feature of marked advantage.

What is claimed is:

1, The combination of a refrigerative plant of the compressor-condenser-evaporator circuit type; a motor for driving the compressor thereof a heat-exchanger external to said circuit and subject to heat produced by degeneration of mechanical energy supplied through the motor to the plant; and means capable of being made effective while the compressor runs and serving, when effective, to connect the compressor discharge with the evaporator and to connect the compressor suction to withdraw liquid from the evaporator through said heat-exchanger.

2. The combination of a refrigerative plant oi' the compressor condenser evaporator circuit type; means external to said circuit for accumulating waste heat generated as an incident to operation of the plant; and means capable of being made effective while the compressor runs and when effective serving to connect the compressor discharge to the evaporator, and to connect the compressor suction to withdraw liquid from the evaporator through a path .which is in heatexchange relation with said heat accumulating means.

3. The combination of a refrigerative plant of the compressor condenser evaporator circuit type; means for accumulating at least a portion of the heat rejected through the condenser; and means capable of being made effective while the compressor runs and when effective serving to connect the compressor discharge to the evaporator and to connect the compressor suction to withdraw liquid from the evaporator through a path which` is in heat-exchange relation with said heat accumulating means.

4. The combination 0f a refrigerative plant of the compressor condenser evaporator circuit type; a motor connected to drive the compressor, and of a type which generates waste heat as an incident to its operation; means for accumulating at least a portion of said waste heat;v and means capable of being made effective while the compressor runs and when eiective serving to connect the compressor discharge to the evaporator and to connect the compressor suction to withdraw liquid from the evaporator through a path which is in heat-exchange relation with said heat accumulating means.

5. The combination of a refrigerative plant of the compressor condenser evaporator circuit type, including a combined motor-compressor unit; a heat exchanger external to the circuit and subject to heat generated by said unit; and means capable of being made elective while the 5 said heat exchanger.

SAMUEL P. SOLING.

REFERENCES CITED The following references are of record in the fileof this patent:

UNITED STATES PATENTS Name Date Ruppricht Aug. 5, 1936 Number 2,049,625 

